Thursday, October 12, 2017

Finding 3-phase is difficult, convincing the owner of the said supply to test some home made hardware is even more so. After building a 3-phase energy monitor my testing options for it appeared very limited. So I set about making my own low-cost 3-phase energy monitor calibration system. Here are some build photos.

Initial testing with DSO scope

Arduino code and Sine-wave table

The main protagonists of this build are the Teensy 3.2 and MCP4728 4-channel I2C DAC. The Teensy pushes an integer valued sine-wave array into the DAC which is then RC-filtered and amplified via some opamps.

With target energy monitor

Eventually I worked up a budget to buy myself a 4-channel Rigol scope from Emona. This showed the nice equal amplitude and properly phased 50-Hz waveform the DAC was producing.

3-phase voltages on oscilloscope

There is more of a backstory and details about this project in the DIYODE Magazine article. I have tested this a fair bit now as well with ATM90E36 Energy Monitor IC and will look at adding power opamps and transferring to a PCB. Below is a video of a 3-phase energy monitor test rig using synthesized waveform vs 12V AC-AC transformer.